Welcome, amigo. I hope your first trip is fun, safe, and successful. The water won't make you sick if you wash your dishes with it or anything like that, although there may be some sediment due to recent rains and snow melt, depending on how soon you intend to go.

What kind of advice are you looking for? A word of caution... you are likely to get more advice than you need

If your going to drink water from a stream, make sure you purify it with purification tablets (or boiling it). It's also a good idea to scoop water up into a towel or shirt to filter out any loose sediment.

Take your time driving into Cataloochee, because the road engineer's philosophy was one good turn deserves another. There is not a lot of room for error on the gravel portion of the road. If you're planning on going in three weeks, keep an eye on the weather. I hate to even mention the word snow, but it is not out of the possibility that time of the year. I camped there during the last week of April a few years ago in the snow. Cool or even cold nights (as in the 20's) are highly possible.

Bear, elk, and a few boar are in Cataloochee. The bear won't bother you if you don't bother them or inadvertently invite them over for snacks. Hang your food supply. Snakes shouldn't be an issue that early in the year. However timber rattlers and copperheads are present. As for planning on fishing all the tributaries in Cataloochee, you'll never do it in 3-4 days. You should have a large time on your trip, it's one of my favorite locations in the park.

I do plan to filter my water. I have a Hiker Pro. Do y'all suggest chemical treatment in addition to the filter?

I have used an old Sweetwater Guardian (now called a MSR Sweetwater) Filter in Cataloochee and elsewhere in the Smokies, and I've never had any problems. I personally don't think chemical treatment in addition to filtration is necessary, but that's just my opinion.